GLTFLoader: add getDependency( type, index ) implementation (#24252)
GLTFLoader: add getDependency( type, index ) implementation (#24252)

* add getDependency('light') implementation

* switch to getDependency ( type, index ) instead of special case getDependency ( 'light' )

* implement getDependency for the light extension
mrdoob/three.js,mrdoob/three.js